Question 878375
You can complete the square or use the quadratic formula.
Quadratic formula:
{{{x = (-b +- sqrt( b^2-4*a*c ))/(2*a) }}} 
{{{x = (-(-5) +- sqrt( (-5)^2-4*3*(-6))))/(2*3) }}}
{{{x = (5 +- sqrt( 25+72))/6 }}}
{{{x = (5 +- sqrt( 97))/6 }}}
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Completing the square:
{{{x^2-4x-7=0}}}
{{{(x^2-4x+4)-7=4}}}
{{{(x-2)^2-7=4}}}
{{{(x-2)^2=11}}}
{{{x-2=0 +- sqrt(11)}}}
{{{x=2 +- sqrt(11)}}}